Sum Cols

L = [[1,1,1,1,1,1,1],
     [2,4,4,2,1,2,4],
     [1,1,1,1,1,1,1],
     [1,1,1,1,1,1,1],
     [1,1,1,1,1,1,1],
     [1,1,1,1,1,1,1]]

def sum_cols(L):
    horz_lng = len(L[0])
    vert_lng = len(L)

    col = 0
    sums = []

    for y in range(horz_lng):
        col = 0
        for x in range(vert_lng):
            col += L[x][y]
        sums.append(col)
    return sums

print(sum_cols(L))